2. Field of the Invention
The invention is related to hand-held power tool, in particular a cordless power tool.
2. Advantages and Summary of the Invention
The present invention proposes a hand-held power tool, in particular a cordless power tool, having a torque-limiting device that is provided for setting a maximum torque that a motor output is able to transmit to a tool-driving element, and having a spring mechanism equipped with at least one first disk spring. The at least one disk spring acts on at least two detent mechanisms arranged in a circumference direction. In this context, a “torque-limiting device” should in particular be understood to be a device that is provided to set a maximum torque, the torque being transmitted, in at least one operating state of the hand-held power tool, by means of a motor output such as an armature shaft and/or a planetary gear set to a tool-driving element and/or a tool holder, for example in the form of a drill chuck or a socket for a hexagonal screwdriver bit in an output spindle. In this context, a “limitation” of the torque should in particular be understood to mean that the torque-limiting device can be used to set the torque that must be reached or exceeded in order for a clutch to react and/or for a transmission of torque from the motor output to the tool-driving element to be limited, particularly in that brief interruptions in the torque occur at intervals when an overload state occurs. In addition, a “detent mechanism” should in particular be understood to be a device, which, in at least one operating state—in particular such as an overload state—performs its function by means of a detent engagement procedure that stops a rotary driving of a tool, for example in the form of a drill bit or a screwdriver bit. The two detent mechanisms are preferably spaced apart from each other in the circumference direction, in particular equidistantly, around the output spindle. Basically, however, it is also conceivable to provide any number of detent mechanisms deemed to be structurally useful and advantageous by the person skilled in the art. In this context, the verb “to act on” should in particular be understood to mean that the disk spring is in contact with at least two detent mechanisms and in particular, is in direct contact with one component of each detent mechanism, and/or that a flux of force travels from the disk spring in the direction of the detent mechanisms without an interposed component. In addition, the disk spring acts on the detent mechanisms axially in the direction opposite from an output direction. In addition, “provided” should be understood to mean especially equipped and/or embodied.
The embodiment according to the invention makes it possible to achieve a space-saving and parts-saving torque-limiting device of the hand-held power tool since in particular, it is possible to dispense with components such as spring supports or washers that are built into conventional transmissions. This makes it possible to simplify assembly, thus advantageously achieving savings with regard to assembly complexity and costs.
According to another proposal, each detent mechanism has at least one first detent element. A “detent element” should in particular be understood to be an element that performs the detent action in the process of a detent engagement and/or disengagement and/or that is moved in the process of the detent engagement and/or disengagement and/or is brought by this movement into a position that prevents or disconnects the rotary driving of the tool-driving element. It is essentially conceivable for this to be any element that is deemed suitable by the person skilled in the art and can be used as a detent element, for example blocks, balls, rollers, and/or combinations thereof. The detent element can be used to produce a structurally simple, reliable torque-limiting device.
Advantageously, at least the first detent element is embodied in the form of a rolling element. In this context, a “rolling element” should in particular be understood to mean any element that is deemed suitable by the person skilled in the art and is capable of executing a rolling motion, for example a drum, a roller, a barrel, a needle, a cone, and/or in particular a ball. Preferably, all of the detent elements are embodied in the form of rolling elements, particularly in the form of balls. The implementation of the detent elements in the form of rolling elements makes it possible to achieve an embodiment of the detent mechanism that is not only advantageously space-saving but also has a particularly long service life.
It is also advantageous if the hand-held power tool, or more specifically each detent mechanism, has at least one additional rolling element that is situated on a side of the at least one detent element oriented toward the disk spring. Each detent mechanism thus has two rolling elements situated axially one behind the other in the output direction. In this case, this additional rolling element represents the component of the detent mechanism that is acted on directly by the disk spring and/or is directly contacted by it. This rolling element also directly contacts and/or acts on the first detent element and/or is likewise embodied in the form of a ball. In general, however, it would also be conceivable for the rolling element to have any of the other embodiments cited above. The additional rolling element permits a distance to be bridged from the disk spring to the first detent element and/or a flux of force to be transmitted from the disk spring to the first detent element, both in a structurally simple, inexpensive, and reliable way.
It is also advantageous if the hand-held power tool has a guide device that fixes at least the first detent element in at least one circumference direction. In this context, a “guide device” should in particular be understood to be a device that predetermines a movement direction, in particular of the detent element, and/or that limits a movement of the detent element in a particular direction, namely a circumference direction along a circumference of the working spindle. In this context, the verb “fixes” should in particular be understood to mean a fixing relative to a transmission housing. The guide device is in particular situated on an inside of the transmission housing, i.e. a side oriented toward the working spindle, and is in particular embodied as integral to said inside of the housing; in this context, “integral to” should in particular be understood to mean “of one piece with” and/or “embodied of a single cast with” and/or “comprising a single component with.” Preferably, the guide device is embodied in the form of a groove, which extends essentially parallel to a main extension direction of the working spindle and whose dimension in the circumference direction of the working spindle is slightly greater than a dimension or diameter of the detent element and/or the additional rolling element. The guide device also fixes the additional rolling elements in the circumference direction of the working spindle. The number of guide devices corresponds to the number of detent mechanisms. By means of the guide device, the flux of force can be transmitted from the disk spring to the first detent element in a particularly efficient fashion. In addition, it is thus possible to define a relative position of the first detent element in relation to the additional rolling element and in particular, to reliably maintain this position during operation. In addition, this makes it possible to reliably guide and define the movement of the detent element during an engagement and/or disengagement of the torque-limiting device.
According to another proposal, the hand-held power tool has at least one adjusting element that acts directly on the at least one disk spring. In this context, an “adjusting element” should in particular be understood to be an element that is at least directly coupled to an actuating element of the torque-limiting device and/or is embodied as integral to the actuating element and by means of which, a maximum torque can be set. In this context, an “actuating element” should in particular be understood to be an element such as a button, a switch, a rocker, and/or in particular a rotatable collar that a user can adjust, in particular manually. The embodiment according the invention makes it possible for a direct adjustment of the maximum torque to be embodied in a structurally simple, direct fashion, without an interposed component, thus yielding a parts-saving and consequently inexpensive embodiment of the torque-limiting device and the hand-held power tool. In addition, the direct action results in an advantageous flux of force from the actuating element to the torque-limiting device. In addition the direct action and the savings in terms of the number of parts make it possible to achieve a short overall length of the torque-limiting device, which has a direct, advantageous effect on the low weight of a hand-held power tool. In addition, the hand-held power tool is particularly rugged in withstanding mechanical impacts.
It can also be advantageous if the adjusting element is equipped with a thread that is provided to adjustably interact with a thread of a transmission housing. In this context, a “transmission housing” should in particular be understood to be a housing in which at least one transmission, e.g. a planetary gear set, is supported or accommodated; the transmission housing preferably encompasses at least most of the transmission, specifically more than 50% of it and in particular, more than 90% of it. In particular, the transmission housing can be composed of multiple parts, thus making it possible to assure a simple assembly. In this context, “interact with” should in particular be understood to mean “engage with”. Preferably, the thread can be used to set the maximum torque. By means of the thread of the adjusting element and the matching thread of the transmission housing, the torque adjustment can be carried out in a structurally simple, reliable fashion. Basically, however, it is also conceivable for the adjusting element to have a thread that interacts with a thread of another component deemed suitable by the person skilled in the art, in particular such as an actuating element.
An advantageous space-saving design can be achieved if the spring mechanism has at least one additional disk spring. Basically, however, it would also be conceivable to provide any number of springs and/or disk springs deemed suitable by the person skilled in the art. Furthermore, it is possible to minimize fluctuations in a solid compression length and in a field of force of the spring mechanism.
It is also preferable for at least the first disk spring and the additional disk spring to be connected in series. In this context, “connected in series” should in particular be understood to mean that in the main extension direction of the working spindle, the disk springs are situated axially one behind the other, particularly with their concavities facing in alternating directions. This arrangement makes it possible to achieve a space-saving design and an advantageously rigid geometry of the torque-limiting device. In addition, a desired spring force can be produced on a short axial spring path. Basically, however, it is also conceivable to provide other arrangements of disk springs; in particular, it is also possible for at least two disk springs situated one behind the other to be oriented with their concavities facing in the same direction and/or it is also conceivable other at least partially parallel disk spring arrangements deemed suitable by the person skilled in the art to be provided, which can be used alone or also in combination with disk springs arranged in series.
A preferred modification is constituted by the fact that the first disk spring and the additional disk spring have different spring characteristics, making it possible to achieve a more beneficial, in particular nonlinear or discontinuous clutch force progression of the torque-limiting device, which directly results in a broad clutch force spread. In addition, the use of differently acting disk springs in the spring mechanism makes it possible to easily adapt the adjusting characteristic of the torque-limiting device to different hand-held power tools or different lines of hand-held power tools such as cordless screwdrivers, cordless drill/drivers, cordless impact drill/drivers, or any other hand-held power tool deemed suitable to the person skilled in the art, thus yielding advantageously variable forces or adjustment possibilities for the spring mechanism.
According to another embodiment of the invention, the first disk spring and the additional disk spring have different material thicknesses. In this context, a “material thickness” should in particular be understood to be a dimension of a disk spring perpendicular to its circular surface and/or essentially in the direction of the main extension of the working spindle. By varying the material thicknesses of the disk springs, it is possible to embody the torque-limiting device in a structurally simple, inexpensive fashion. In general, however, it would also be conceivable for them to have a uniform material thickness, with the springs being arranged in layers, partially in parallel and partially in series.
According to another proposed embodiment, the first disk spring and the additional disk spring have different outer diameters and/or inner diameters. In this case, varying the outer and/or inner diameter of the disk spring(s) makes it possible to shorten and/or lengthen a lever arm between force exertion points of the detent element and/or the first disk spring and/or the additional disk spring and/or the adjusting element. The different outer and/or inner diameter makes it possible to achieve a desired spring force of the spring mechanism with a short spring path and to achieve a structurally simple embodiment.
According to another proposed embodiment, a harder-acting disk spring is positioned on a side of the spring mechanism oriented toward the detent element. In this context, a “harder-acting disk spring” should in particular be understood to mean that the disk spring has a greater spring constant than the additional disk spring and in particular, greater than all of the other springs of the spring mechanism. The term “positioned” here in particular means that the harder-acting disk spring directly contacts the detent element. This positioning makes it possible for a compressive load exerted on certain points of the detent element to be favorably transferred to the spring mechanism.
It is also possible for a softer-acting disk spring to be situated on a side of the spring mechanism oriented away from the detent element. In this case, this disk spring is in particular advantageously situated in direct contact with the adjusting means as a result of which a line load on the adjusting means, particularly in an overload state of the torque-limiting device, is converted to a surface load, which in turn results in a spreading of the line load of the adjacent spring or more specifically, of the softer-acting spring. Preferably, a contact line between the disk spring and the adjusting element is situated on a side of the disk spring oriented in the radial direction toward an adjusting thread.
A solid compression of the spring mechanism advantageously results in a blocking of the torque-limiting device. In this context, “solid compression” should in particular be understood to mean that an action of the spring mechanism has been nullified. By contrast with a conventional torque clutch, a direct solid compression of an adjusting element with a detent element can produce a more reliable torque-limiting device since it is possible to avoid disadvantageously high tolerances. It is also possible to avoid failure at high torques. Furthermore, by comparison with prior-art embodiments in which detent elements are locked directly in relation to each other, it is possible to achieve savings with regard to parts, space, and costs, which allows the size of a hand-held power tool to be reduced, making it possible to work in cramped conditions and small spaces. In addition, the disk springs can be used to manufacture a solid compression height of the spring mechanism in a particularly inexpensive, very strictly toleranced fashion. It is also possible to create a reliable locking of the torque-limiting device by means of low axial production tolerances and a rigid geometry. Moreover, it is possible to achieve short axial strokes between a locking position and a minimum clutch setting of the torque-limiting device. It is also possible to achieve a high degree of resolution or gradation at low clutching forces and a low degree of resolution or gradation at high clutching forces.
It is also advantageous if the torque-limiting device has at least one clutch that is embodied as at least partially integral to at least one component of a planetary gear set. In this context, “integral to” should in particular be understood to mean that the clutch can be separated from the planetary gear set only with a functional loss and/or that at least one component of the clutch and one component of the planetary gear set are comprised of one and the same component. The expression “at least partially” means that at least one component, e.g. a ring gear of the planetary gear set, is integral to the clutch. In this context, a “clutch” should in particular be understood to mean an interaction of one component device—in particular the detent mechanism or detent element of the detent mechanism—with a cam track in an upper surface of the ring gear, which at intervals, temporarily interrupts the flux of force when the set maximum torque is exceeded. The integral embodiment of the clutch makes it advantageously possible to achieve savings in terms of space, parts, and costs.